This invention relates to improvements in a servomotor and more particularly to improvements for a fluid pressure servomotor used to operate the hydraulic brake systems of motor vehicles.
As well known in the art, conventional servomotors of the fluid pressure type have utilized a diaphragm secured to a power piston for forming pressure chambers in the housing of the servomotor. The power piston generally is made from a heat-resisting synthetic resin material. In order to secure the diaphragm, a retainer is placed on the power piston and turned so that the inner portion of the diaphragm is tightly sandwiched between the retainer and a disc-like portion of the power piston. The retainer is then maintained in position by hooking a plurality of projections formed on the inner periphery of the retainer on a plurality of projections formed on the outer periphery of a boss of the power piston.
However, in turning the conventional retainer to lock it into position, it is easy to rupture of initiate cracks on the inner portion of the diaphragm and thereby loose the seal between the diaphragm and power piston.
Furthermore, since projections must be provided on the power piston, a mold must be used for forming the power piston which is dividable into two portions along the axial line of the power piston. Because of difficulty in the cutting and processing work on the synthetic resin material from which the piston is formed, a deburring operation is also needed after formation of the power piston. These operations add significantly to the manufacturing cost.
Accordingly, it is a primary object of this invention to provide improvements in a servomotor that eliminate the aforementioned drawbacks in the conventional servomotor.
It is a further object of this invention to provide improvements in a servomotor for securing a diaphragm to a power piston uniformly and ensurely.
It is still another object of this invention to provide an improved servomotor that can be very economically manufactured while ensuring proper securing of the diaphragm to the power piston.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the foregoing objects and in accordance with the purpose of the invention, as embodied and broadly described herein, the improvements in the sevomotor of the invention comprise (1) a housing; (2) an annular diaphragm having its outer periphery sealingly attached to the housing; (3) power piston means axially movable within the housing and having (a) a boss axially extending through the annular diaphragm, the boss including a bore and an opening radially-extending from the bore to the outer periphery of the boss adjacent the diaphragm; and (b) an external flange extending radially from the outer periphery of the axially extending boss for positioning adjacent the diaphragm, and wherein said annular diaphragm and the power means form first and second pressure chambers in the housing; (4) valve means for regulating pressure in the first and second pressure chambers, the valve means including a valve member slidably and sealingly disposed in the bore and having an engaging groove in its outer periphery; (5) retaining means for coupling the diaphragm against the flange of the power means, the retaining means including (a) an axially extending cylindrical seat in which the boss is tightly positioned, and wherein the seat has a radial opening, and (b) an external flange radially extending from said seat for pressing an inner portion of the diaphragm against the flange of the power piston means when the retaining means is in a predetermined coupling position and wherein the radial opening of the seat coincides in a radial direction with the radially extending opening of the boss and the engaging groove of the valve member when the retaining means is in the predetermined coupling position; (6) pin means positioned in the openings of the retaining means and boss and the engaging groove of the valve member for locking the retaining means in the predetermined coupling position; and (7) means for maintaining the pin means in position.
The invention consists in the novel parts, constructions, arrangements, combinations and improvements shown and described. The accompanying drawings which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the principles of the invention.